The weather rarely bothers me; in fact, I love shooting on cold, crisp nights. When most people would rather be bundled up inside, you'll find me out in the clean, clear air searching for beautiful scenic photos. When it's cold and crisp, the air is generally clean and clear, which makes for images that "snap". When there is humidity in the air or that haze that comes with summer heat, your photos can look fuzzy or even out of focus. Certainly, you can take beautiful images in any conditions, but I really love the clarity that comes from shooting in the cold and I never mind throwing on another layer to prepare for the elements.
Lower Manhattan photographed from Brooklyn Heights. ISO 200, 15 sec. at f16, 35mm lens